Clinical progression of transplanted large granular lymphocytic leukemia in Fischer 344 rats exposed to 60 Hz magnetic fields

The purpose of this study was to determine if 60 Hz magnetic fields can alt er the clinical progression of leukemia in an animal model. Large granular lymphocytic (LGL) leukemia cells from spleens of leukemic rats were transpl anted into young male Fischer 344 rats, producing signs of leukemia in appr oximately 2-3 months. The animals were randomly assigned to 4 treatment gro ups (108/group) as follows: 1) 10 G (1.0 mT) linearly polarized 60 Hz magne tic fields, 2) sham exposed [null energized unit with residual 20 mG (2 mu T) fields], 3) ambient controls [<1 mG (0.1 mu T)1, and 4) positive control s (a single 5 GL whole body exposure to Co-60 4 days prior to initiation of exposure). All rats were injected intraperitoneally (ip) with 2.2 x 10(7) LGL leukemic cells at the initiation of exposure or sham exposure. The magn etic fields were activated for 20 h/day, 7 days/week, allowing time for ani mal care. The experimental fields were in addition to natural ambient magne tic fields. Eighteen rats from each treatment group were bled, killed, and evaluated at 5, 6, 7, 8, 9, and 11 weeks of exposure. Peripheral blood hema tological endpoints, changes in spleen growth, and LGL cell infiltration in to the spleen and liver were measured to evaluate the leukemia progression. No significant or consistent differences were detected between the magneti c field exposed groups and the ambient control group, although the clinical progress of leukemia was enhanced in the positive control animals. These d ata indicate that exposure to sinusoidal, linearly polarized 60 Hz, 10 G ma gnetic fields did not significantly alter the clinical progression of LGL l eukemia. Furthermore, the data are in general agreement with previous resul ts of a companion repeated-bleeding study in which animals were exposed for 18 weeks. (C) 1999 Wiley-Liss, Inc.